A method for determining the atmospheric pressure on the basis of the intake pressure measured downstream of an air filter in an intake line of an internal combustion engine, and of the air mass flow rate measured downstream of the air filter, and optionally of the intake air temperature. The calculation of the atmospheric pressure and the calculation of a degree of contamination of the air filter are separated by standardizing the measured air mass flow rates at two predefined values. Furthermore, during the calculation a characteristic curve for the degree of contamination of the air filter as a function of the determined pressure difference at the predefined air mass flow rates is used, and a characteristic diagram for the degree of contamination of the air filter as a function of the standardized air mass flow rate and of the determined pressure difference is used.